The proposed work will result in an evaluation of heart rate variability as an additional parameter of fetal monitoring. Short-term (50 to 250 cycles per minute) and long-term (5 to 50 cycles per minute) variability will be measured continuously during monitored labor and delivery, and the magnitude of each will be correlated against intensity of uterine activity and type and severity of heart rate decelerations. Longer range trends of variability will be studied and compared against the one-minute Apgar score and its components. An on-line computer system will be used to measure variability and for pattern-recognition in the fetal monitoring record. A comparison will be made of a variety of computational formulae for the quantification of variability. Correlations between variability and other indicators of fetal distress will test the validity of prognostic use of beat-to-beat variability. The description of its course in a series of patients will establish norms for its clinical interpretation.